Agriscience teachers help support the mission of the American Floral Endowment to inspire people to pursue careers working with plants by providing curricula related to ornamental horticulture. Nevertheless, an overall understanding of how the horticulture industry is connected to the studies of science, technology, engineering, and mathematics (STEM) has left a shortage of skilled professionals. A professional development program was designed to provide agriscience teachers with experiences focused on STEM concepts taught in horticulture and floriculture curricula. The Science Teaching Efficacy Belief (STEB) instrument was used before and after the three days of content specific inquiry-based instruction to determine participants' perceptions of their performance pre, post, and post-post. While teachers showed growth in their mean scores for the Science Teaching Outcome Expectancy (STOE) and Personal Science Teaching Efficacy Beliefs (PSTEB) constructs of the STEB between all three testing periods, no significant difference was found across the period-of-time. It is recommended that teacher educators consider how to create professional development experiences for agriscience teachers that target content to positively impact teacher self-efficacy. Further, it is recommended that professional development opportunities contain follow-up communication to determine whether teachers utilize curricular resources and ascertain how the teacher's new knowledge is transferred to inform instructional change. The final recommendation is to measure student learning outcomes as a result of content-specific teacher professional development.